1. Field
This invention relates generally to the field of solid phase radioimmunoassay of T.sub.3 or T.sub.4, and specifically to reagents useful in such assays.
Radioimmunoassay (RIA) is a term used to describe any of several methods for determining very low concentrations of substances (especially in biological fluids), which methods are based on the use of radioactively labelled substances which can form immunochemical complexes. A typical RIA is based on the observation that a known amount of a radioactively labelled substance (against which there exists antibodies) will tend to compete with an unknown amount of that substance (unlabelled) for a limited number of complexing sites on the antibodies. Thus, such a RIA is performed by adding a known amount of labelled substance and a fluid containing an unknown amount of the substance (unlabelled) to a given amount of antibodies to the substance. During a suitable incubation period, complexes of both antibody-substance (unlabelled) and antibody-substance (labelled) are formed. These complexes are then separated from the reaction medium and radioactivity counts are taken of either the removed complexes or the remaining solution. These counts can be used to determine the unknown concentration by known means.
It can be appreciated that an essential step for such a RIA involves the separation of complexed products from the incubation medium. This separation step is greatly facilitated by using antibodies which have been attached to essentially water-insoluble carrier materials. The technique for the use of such materials has become known as solid phase radioimmunoassay or SPRIA. The present invention discloses novel reagents which can be used in the SPRIA of either T.sub.3 or T.sub.4.
2. Prior Art
To date, there are a wide variety of radioassay "kits" available commercially for determining concentrations of T.sub.3, T.sub.4, and/or combinations of those substances. See, for example, the recent directory listing "Radioassay Test Kits and Components", Laboratory Management, September, 1974, pages 29-42. Generally, the use of such kits is based on the affinity of T.sub.3 or T.sub.4 (labelled, for example, with I.sup.125) for anti-T.sub.3 or anti-T.sub.4 antibodies. All such kits require a sequence of assay steps some of which are subject to operator error in preparation and/or measuring of the various reagents needed for a given test.
Although it can be appreciated that the use of SPRIA techniques can reduce some of the steps, such techniques still require separate steps for preparing or mixing the immobilized antibody, adding a precise amount of labelled material (tracer), adding an unknown sample, incubating, separating, and counting. Each of these steps is subject to operator error. It is an object of the present disclosure to provide a simplified SPRIA for T.sub.3 and T.sub.4 which requires less operator steps because of the novel reagents used. The method and reagents are disclosed in detail hereunder.